Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

Bear bottom line you have mentioned a dollar figure several times and for that range, I nor any QUALITY contractor would not touch your job for even the most basic system. You should be budgeting for 2.5 to 3 times that amount minimum Unico w/chiller 20% to 30% more.

I have done several SIP (sandwiched insulated panels) homes ICF and various other very tight homes, I am BPI certified and NCI certified with better than 40 years experience. I have also gone into dozens of similar homes to fix comfort and efficiency problems, all had too much capacity most grossly oversized. I generally need to reduce capacity and airflow as well as increase supply ductwork capacity and return capacity and install Supplemental dehumidification.

I will go over a SIP home I did 5 or 6 years back, 2800 sq.ft. 2-story. We installed a Bryant (Carrier) Evolution 2-ton2-stage unit with a 3-stage heat strips ECM 3.0 blower with Evolution controls w/2-zones all metal duct w/Ultraire 350 supplemental dehumidifier w/digital controller & standard HiEff electric water heater on a timer. The Dehum is scheduled only to operate during occupancy. They maintain 78* 48% RH and their highest electric bill has been less than $90.00.

I would recommend a similar system for you, stay away from gas heat even the HP would more than likely be overkill.

Bear bottom line you have mentioned a dollar figure several times and for that range, I nor any QUALITY contractor would not touch your job for even the most basic system. You should be budgeting for 2.5 to 3 times that amount minimum Unico w/chiller 20% to 30% more.

I appreciate the spirit of what you've written, especially since forum rules preclude talking pricing, which is what I, or any homeowner, would really want to discuss. If you re-read what I've written, I've never mentioned a specific dollar figure as my budget. What I've been talking about are premiums (or premia for the latin snobs). Simple finance:
$10,000 at 4% for 30 years = $47.74/month
$10,000 at 4.5% for 30 years = $50.67/month

If I can save $50 on my operating costs, then spending up to $10,000 more on capital costs is, at worst, a wash. If I spend $5k extra in acquisition costs in order to save $50/month on my power bill, then I am ahead and the premium was worth it from a strict financial perspective. The emotion comes into play when factoring in convenience and comfort, but let's assume that I can afford comfortable as a baseline.

Point #2: simple consumer behavior: I don't spend $10k without knowing a lot about something. I don't spend a large multiple of $10k without knowing as much as I can about something (e.g., building a home).

I have done several SIP (sandwiched insulated panels) homes ICF and various other very tight homes, I am BPI certified and NCI certified with better than 40 years experience. I have also gone into dozens of similar homes to fix comfort and efficiency problems, all had too much capacity most grossly oversized. I generally need to reduce capacity and airflow as well as increase supply ductwork capacity and return capacity and install Supplemental dehumidification.

I will go over a SIP home I did 5 or 6 years back, 2800 sq.ft. 2-story. We installed a Bryant (Carrier) Evolution 2-ton2-stage unit with a 3-stage heat strips ECM 3.0 blower with Evolution controls w/2-zones all metal duct w/Ultraire 350 supplemental dehumidifier w/digital controller & standard HiEff electric water heater on a timer. The Dehum is scheduled only to operate during occupancy. They maintain 78* 48% RH and their highest electric bill has been less than $90.00.

I would recommend a similar system for you, stay away from gas heat even the HP would more than likely be overkill.

I would be happy averaging a $100/month power bill with great temperature and humidity control.

This has been a big question mark with the ducted VRFs. There is a minimum efficiency spec, but it is hard to discern how to compare that versus a 'standard' system. It sounds like the price premium is significant with a minimal performance improvement, esp. vs. domestic brands, if any.

It's really the filters. That, and I think that mini-splits are mostly for elevators around here.

Any specific recommendations beyond UNICO? I've not even heard of mini-chillers until it came up here. I thought chilled water systems were strictly for the Big Boys.

Chilled water has historically been just for the big boys - mainly because the residential market hasn't asked for it. It provides much better comfort and flexibility than just about any 'conventional' residential system. To this day, the only reason there isn't more chilled water in residential is simply because most residential techs don't get it yet. There are a few companies (unico being one of them) that are trying to market it to the home. The problem is, the big guys make most their money on track homes, and track homes make most their money on just the simplest/fastest means to a sale. Some other mini-chiller companies are Waterfurnace and Multiaqua. I think the biggest advantage of chilled water is going to be the zoning and elimination of ducting. A few in-wall or in-ceiling fancoils are all that is needed. If done with domestic water for heating, you can even have perfect humidity control.

If the direct unico dealer doesn't end up working out, another option might be to look into an outfit that does both commercial and residential - they may be able to work between the different sides of their shop to put together a great system for you. Because of the rare nature of the work, first cost may end up being higher, but then end returns will be excellent comfort, and upper tier efficiency. To help steer them in a proper direction, some key components would be a few different zoned fan coils, a single chiller, and a buffer tank to stretch out cycling time of the chiller. Insulated PEX tubing is very versatile and useful for this type of system. Other key benefits of using a hot water heating/reheating system is, you can work it with the domestic hot water, and get the benefits of continually circulated hot water as well, for that good instant hot effect.

Some other mini-chiller companies are Waterfurnace and Multiaqua. I think the biggest advantage of chilled water is going to be the zoning and elimination of ducting. A few in-wall or in-ceiling fancoils are all that is needed. If done with domestic water for heating, you can even have perfect humidity control.

If the direct unico dealer doesn't end up working out, another option might be to look into an outfit that does both commercial and residential - they may be able to work between the different sides of their shop to put together a great system for you. Because of the rare nature of the work, first cost may end up being higher, but then end returns will be excellent comfort, and upper tier efficiency. To help steer them in a proper direction, some key components would be a few different zoned fan coils, a single chiller, and a buffer tank to stretch out cycling time of the chiller. Insulated PEX tubing is very versatile and useful for this type of system. Other key benefits of using a hot water heating/reheating system is, you can work it with the domestic hot water, and get the benefits of continually circulated hot water as well, for that good instant hot effect.

Good post here. I've used MultiAqua in commercial setting. The smallest heat pump they had when I used it was 5 tons, but they have smaller air cooled chillers (cooling only). Buffer tank is a good idea in these smaller capacity systems. Even if you don't use PEX throughout, it can be used for final connections to equipment to simplify installation. I was thinking the same thing about seeking a commercial outfit that does some high end residential. They know how to handle chilled water systems and some can do VRF if you go that route.

The Mitsubishi VRF system will also do water to water as well which means you could mix conventional systems and chilled water with a modulating condenser.

+1 on a buffer tank. You really have to manage short cycling for equipment life, comfort and effciency. a 8-10F water temp swing is hardly ideal for comfort. A 5 minute run time is a bare minimum, but ideally you want 10-15 minutes run time. You need soem storage for that durign low load conditions. The tank should also be tall enough to provide some stratification in the tank to get the highest return temps possible for effciency. Also don't be a afraid to oversized distribution piping, since it too can be a source of water storage. With Pex, going up a size isn't a big price increase and will reduce pump power consumption as well. The simpliest control scheme is a vairable secondary pump with fixed pressure and zones valves. Same with the hot water for the boiler.

The absolute best system you can install is hot and chilled water. You can even use higher temp chilled water to cool the floors, so long as they stay above the dewpoint indoors. Pretty easy to do if they are piped in series with the chilled water return and use a 3 way valve and it's own circulator.

We could see huge energy savings and comfort in the US if we actually looked at installing chilled and hot water as a central utility just like electricity. Of course it would make it even easier for hacks to do residnetial work, since refirgeration would be out of the mix. They could slap in a vairable circulator or multispeed circulator and they are good.

The Mitsubishi VRF system will also do water to water as well which means you could mix conventional systems and chilled water with a modulating condenser.

+1 on a buffer tank. You really have to manage short cycling for equipment life, comfort and effciency. a 8-10F water temp swing is hardly ideal for comfort. A 5 minute run time is a bare minimum, but ideally you want 10-15 minutes run time. You need soem storage for that durign low load conditions. The tank should also be tall enough to provide some stratification in the tank to get the highest return temps possible for effciency. Also don't be a afraid to oversized distribution piping, since it too can be a source of water storage. With Pex, going up a size isn't a big price increase and will reduce pump power consumption as well. The simpliest control scheme is a vairable secondary pump with fixed pressure and zones valves. Same with the hot water for the boiler.

The absolute best system you can install is hot and chilled water. You can even use higher temp chilled water to cool the floors, so long as they stay above the dewpoint indoors. Pretty easy to do if they are piped in series with the chilled water return and use a 3 way valve and it's own circulator.

We could see huge energy savings and comfort in the US if we actually looked at installing chilled and hot water as a central utility just like electricity. Of course it would make it even easier for hacks to do residnetial work, since refirgeration would be out of the mix. They could slap in a vairable circulator or multispeed circulator and they are good.

There are district cooling systems in some metro areas, but it takes a certain density level to make the infrastructure worth it. I can potentially see it becoming a reality in some high end residential developments, but it's not something a real developer has caught wind of yet. You could, potentially, work within a neighborhood to develop a co-op to do it, but it would take support from some manufacturers. A highly optimized central plant in a box style design could actually be purchased and deployed at the neighborhood level.

There actually is a LEED draft for a Neighborhood Development Plan that talks about neighborhood level CHP plants, but I am not aware of any developers moving in that direction yet. All neighborhood LEED applicants I've read about are mixed commercial/residential developments with condo's/apartments, not freestanding single family homes. However, the only practical difference between the two is the distance between them, so a little higher firts cost, and little higher pumping load.

I think the biggest advantage of chilled water is going to be the zoning and elimination of ducting. A few in-wall or in-ceiling fancoils are all that is needed. If done with domestic water for heating, you can even have perfect humidity control.

A distributed fan coil system starts to sound like a similar architecture to a mini-split system, just with water as the heat transfer medium, rather than refrigerant. Is this approximately correct?

If I eliminate the central AHU(s), then don't I need a larger quantity of filters as well? We were interested in combinations of electrostatic and UV 'filters', which would seem to be prohibitive to do with more than a couple of AHUs (or equivalents), especially ones sized to fit in-wall or in-ceiling.

I am very curious about how this technology improves dehumidification, though!

A distributed fan coil system starts to sound like a similar architecture to a mini-split system, just with water as the heat transfer medium, rather than refrigerant. Is this approximately correct?

Yes, the fan coils would not be unlike mini-splits - though there are fan coils that can be concealed in walls or ceilings with only the registers showing. Chilled water and hot water are pumped in a loop to the coils, where a valve controls the amount of flow through the coil to smoothly control the amount of cooling. In this way, the cooling can be matched exactly to the demand, eliminating the cycling that a conventional system does.

Originally Posted by Bear_in_HOU

If I eliminate the central AHU(s), then don't I need a larger quantity of filters as well? We were interested in combinations of electrostatic and UV 'filters', which would seem to be prohibitive to do with more than a couple of AHUs (or equivalents), especially ones sized to fit in-wall or in-ceiling.

Potentially. The thing that most homeowners don't realize though, is that the filtration on a residential system is really there to protect the cooling coil from building up blockage, much more than it is there to clean the air in the home. There is no reason you cannot still use central air with chilled water, and you still gain most the benefits of it, by simply using a larger air handler and ducting to spaces conventionally. Chilled water still provides an advantage in this respect, because you can still have multiple zones through motorized dampers that cut back the cold air to individual space. On a conventional system, you are limited in how much you can cut back, because too little air flow through an evaporator can/will result in the evaporator icing up if not enough warm air is provided to it. A chilled water coil, however, is supplied with ~42°F water, and will never ice up, even down to zero air flow.
No matter what system you go with, it is still going to be worth it to have an appropriate amount of outside air change into the home. The way I like to see this done is to draw air out of the areas you already want to draw air out of anyway (bathroom, kitchen, pantry, mudroom, laundry, etc). This allows a single fan to handle all those exhaust streams together, and you can have continuous small air change, keeping those spaces negative to the rest of the house, preventing odor/pollutant propagation, while still changing air. Then you provide a single outside air inlet to a common area of the home, with a dust filter there, or if you do go with a central air handler, have the intake go there.
If high filtration is a major requirement for you, then the central ducted system may be your only viable option, but I would ensure you work with the architect well to make sure all those ducts are in conditioned space, so the duct-work doesn't present itself as a life-long energy siphon. Ask yourself this, though: do you notice a major increase in household dust in the spring and fall when your system isn't running as long (meaning less filtration time), or in the winter when it potentially never turns on at all? The amount of dust removed by a typical HVAC filter, or even advanced UV/ESP systems, because of it's relatively low air change, is nothing compared to the dust removed by simply vacuuming the home weekly.

Originally Posted by Bear_in_HOU

I am very curious about how this technology improves dehumidification, though!

The way you dehumidify air is to cool it below it's dew point. This causes condensation, which is then drained off. In a conventional A/C only system, with little cooling load, but high humidity (Houston, for example), the cooling system runs, removing moisture, but this also makes the space cold, so the system shuts back off. Some of the moisture on the coil then re-evaporates and eventually makes it back into the home (when the unit turns back on). If the cooling load is not there, you will either have to over-cool the space, or simply not remove the moisture. The trick is to cool the air as it passes through the cold coil, removing the moisture, then add heat back in to control temperature. ON a conventional system, where the evaporator is after the furnace, there's no way to do this. A whole house dehumidifier is basically a small refrigeration/air conditioning system, that cools the air with the evaporator, then warms it back up with the condenser. It works great, but is a separate piece of equipment. A chilled water dehumidifier functions similarly, cooling the air with chilled water, and then warming it back up with either hot water, or potentially the warmed up returning chilled water. The advantage chilled water provides here over a mechanical dehumidifier is in the control. It is much steadier, so it is able to equalize out with load, and near perfectly control humidity and temperature, without any sensible variations or cycling. Chilled water's key benefits over conventional mechanical cooling are the versatility, ease of zoning, and overall comfort level through better control.

The biggest advantage of chilled water is that airflow and equipment operation decoupled and the coil temperature is a function of chilled water temp and flow rate. There is no minimum aiflow to keep equipment running, and you humidity removal can be optimized easily. Basically, you vairables of airflow, coil temp and delivered capacity to each zone become independant.

Air cleaning, in my opinion, is a job for a specialized air filteration unit, or mainly the job of a vacuum cleaner to remove dust that has settled on the floor.

I would still suggest a central ventilation system wit ha ERV and if desired a HEPA or at least a media filter. This could still be done usig a small central air handler to distribute the air.

Actually if the "sky's the limit" I would use an air handler unit with an economizer and preheat or cool the incomming air wiith chilled and hot water coils. The conomizer would have a minimum position during occupied periods for fresh air. ERV's are nice, but better overall to pressurize the space. This unit would also be mandatory if you install a large kitchen hood/exhaust fan.